April's wet weather brought respite from the prolonged airborne particle pollution that affected the UK in February and March. Pollution problems in April were mostly short-lived. Traffic caused moderate pollution close to busy roads in London, Glasgow and Dumfries. Both Port Talbot and Scunthorpe experienced moderate sulphur dioxide from nearby steelworks, and Grangemouth suffered pollution from the oil refinery. Polluted air from continental Europe extended over southern England on 5 April and combined with local traffic exhaust to cause moderate air pollution in the coastal towns and cities between Eastbourne and Portsmouth.

Atmospheric pollutants that build up across the northern hemisphere during winter start to react in the increasingly strong spring sunshine. This can cause breaches of World Health Organisation guidelines for ground level ozone. During April this phenomenon led to brief spells of moderate pollution over the UK, most frequently in Scotland, and north-west and south-east England.

On 17 April Southampton's AirAlert system was used for the first time to support the emergency services during a large fire in the Western Docks. Text messages were sent to nearly 200 vulnerable people advising them to stay indoors, with windows closed, as smoke from the fire spread across the city. On 24 April smoke from a fire at a metal recycling yard caused a 10km long pollution plume over north-west London.